The h Bar

0celo7

17:03

Is time orientability completely topological and doesn't depend on the metric at all?

Danu

It's not topological

Hari Prasad

@BernardMeurer I am sorry. But I didn't mean to do that.

Danu

But it's not a notion from Riemannian geometry

Orientations are defined through the tangent bundle

0celo7

@Danu yes, the top degree forms

Danu

So it's not really a topological notion

0celo7

17:12

But maybe @Slereah is hiding a theorem on time orientation

ACuriousMind

@HariPrasad That just cannot be true. I would be willing to believe you are sorry, but you don't just copy stuff without intending to.

0celo7

@Danu time orientation has nothing to do with orientation...

Danu

@0celo7 Ah...

Lame-o terminology :(

Hari Prasad

@BernardMeurer @ACuriousMind yes I agree that I made mistakes in citing answers. I did cite in many answers, But i didn't knew the right way to do so. I am sorry and please don't mistake me

0celo7

Time orientation is a continuous choice of "future"

Regular orientation is a continuous choice of "right handed"

@Danu Well...regular orientation is topological because the existence of an orientation is equivalent to the n-th exterior bundle being trivial

Bernard Meurer

17:17

@0celo7 Help me I'm freaking out dude

0celo7

Off the top of my head I have no clue what the conditions for time orientations are

Bernard Meurer

I can't sleep anymore, not even shitting

0celo7

Besides being able to choose a future vector at each point

Text me

Danu

@0celo7 I guess I don't like to think of statements about bundles built from the tangent bundle as being purely topological, but I guess you can argue about that.

ACuriousMind

@Danu One can define orientability purely through the action of the transition functions on homology classes, no tangent bundle needed

Danu

17:21

@ACuriousMind Ah, neat.

0celo7

Reference?

Hari Prasad

@ACuriousMind Can you please explain to me what quantum fluctuations are?

3

0celo7

Lol.

@ACuriousMind I take it you don't have a neat topological thing for time orientation?

Slereah

17:43

Time orientation isn't purely topological

But IIRC

All lorentzian manifolds admit a time-orientable metric

But

ACuriousMind

@HariPrasad I have never met someone who could define them. Other than saying it's another name for the standard deviation of observables, which does not do all the things commonly attributed in pop-sci literature to these mysterious "quantum fluctuations".

@0celo7 Nope

Slereah

Not all lorentzian manifolds admit a non-time-orientable metric

I think that's the thing?

Like you won't find a non-time orientable metric on $R^4$

Hari Prasad

@ACuriousMind Thanks

Slereah

2

Q: Orientability of spacetime

In many theoretical setups it is implicitly assumed that the underlying manifold (i.e. spacetime) is orientable. Then our analysis depends on this implicit assumption. For example, Stokes' theorem assumes orientability of the chain on which we integrate. However, we accept that time "always" poin...

"In particular, a sufficient condition to guarantee this is that M is simply connected (since any covering map of a simply connected manifold M is trivial). So we have that: a simply connected Lorentzian manifold must be time-orientable. "

user116211

0

Q: Why did Einstein Develop General Relativity?

I know that ultimately GR was validated by experiment. I'd like to know however, if there was any experimental discrepancy at the time that pointed to a conclusive flaw in Newtonian gravity, and which led Einstein to say "Hmm...you know what? Newtonian gravity can't be correct. Let me see what I ...

general-relativity newtonian-gravity

user116211

17:50

JD, where are you?

Hari Prasad

@ACuriousMind Does the Higgs mechanism has anything to do with Quantum fluctuations?

0celo7

@Slereah We'll discuss when I get home...

Danu

@HariPrasad No.

ACuriousMind

@HariPrasad 1. Why would you think so? 2. Why are you asking me?

Hari Prasad

@ACuriousMind 1. I heard that fluctuations in Higgs field gives rise to Higgs Boson 2. We were talking about it for a while now.

Higgs Boson - What You Don't Know: Dan Hooper, Ph.D. at TEDxNaperville

►

user54412

17:58

So I was doing the review queues last night, and I found myself wanting to write this comment:

user54412

> You have yet to post a single intelligible sentence to this site. Everything you say is a mess of incoherent ideas, with almost as many spelling, capitalization, and grammatical errors as there are words. This is a site for professionals. Please stop filling it with garbage.

6

user54412

Would that have been over the top?

Danu

@ChrisWhite Yes

But still 10/10 :)

Hari Prasad

@ChrisWhite yes

ACuriousMind

@ChrisWhite The fact that I know exactly who you're talking about indicates that it would have been correct (but, yes, also over the top)

user54412

18:03

If only there were negative bounties... I could contribute some of my reputation to obliterate others'. Maybe one could even get users suspended by reducing their rep below 0.

user54412

I guess I can only dream about a perfect world

3

ACuriousMind

@ChrisWhite I bet that that could quite quickly lead to some interesting and fragile mutually-assured destruction scenarios

user54412

ah, a question for Worldbuilding then

ACuriousMind

lol

Slereah

@0celo7 Are you my wife now

4

Hari Prasad

18:13

@Slereah lol

Danu

@ChrisWhite I'd be interested to see this.

hubot

Hello there!

barrycarter

Hi, Hubot. I initially thought you WERE a bot!

hubot

Hehehe. No, I'm not bot.

barrycarter

The name threw me off. Good afternoon.

0celo7

18:40

@ACuriousMind Is it bad I don't know who this is?

I don't notice spelling errors for some reason

ACuriousMind

@0celo7 It just shows you don't spend as much time on the site and in the review queues.

0celo7

@Slereah Only if you want to joint my polygamous relationship with @ACuriousMind and @FenderLesPaul

@ACuriousMind I don't review, that's true.

I only troll the GR section, for some strange reason.

ACuriousMind

'cause you're a nerd

Bernard Meurer

I can't get to 1000 rep

I'm stuck at 700 and no questions that I can answer come up

ever

0celo7

@ACuriousMind What are the chances of me rolling with the math major and just becoming a geometer in grad school :/

Bernard Meurer

18:44

@0celo7 1 in 4

ACuriousMind

@0celo7 I have no idea

Bernard Meurer

$$\frac{\pi}{e}$$

that's the probablility

ACuriousMind

edit fail :P

hubot

Do you think concluding from yesterday's discussion that I should begin from Resnick Halliday or other similliar books and then take for Feynman lectures?

barrycarter

You only need a single dollar sign

Bernard Meurer

18:46

@ACuriousMind It eventually worked

@barrycarter I want two to make it big

barrycarter

@BernardMeurer No, it didn't.

Hari Prasad

@BernardMeurer $\frac{\pi}{e}$

Bernard Meurer

@barrycarter It shows pi over e nicely here

barrycarter

I have MathJax turned on ...

Hmmm

Bernard Meurer

@barrycarter What abou chatJax?

@barrycarter You need chatJax magic

barrycarter

18:47

Oh, NM, I thought I did but I didn't.

ACuriousMind

Displays properly (that is, as an unnecessarily display-style equation) here

barrycarter

It's on now.

/me laughs.

hubot

/me laughs

barrycarter

I am now suitably amused by your greater than 1 probability joke.

hubot

I've written it and nothing

barrycarter

18:49

It doesn't work, I was experimenting.

Bernard Meurer

$$ S A V A G E $$

Hari Prasad

@Slereah any new songs?

0celo7

19:43

Is a white car girly?

hubot

0celo7: I don't think so.

Assignment to color sexual features is non-logic.

0celo7

Lol

hubot

It doesn't matter.

0celo7

Lol

You're pretty weird to say that ;)

hubot

Let's talk about something normal eg. physics, maths.

0celo7

19:50

What?

There's more to life than math and physics

barrycarter

@0celo7 Not really. Everything is math.

0celo7

Lol

hubot

Physics is so obvious in our life that people people don't notice it for example gravitational law

ACuriousMind

Apr 15 '15 at 20:01, by ACuriousMind

Joy in life is worth more than an understanding of bundles :P

Apr 15 '15 at 20:02, by 0celo7

@ACuriousMind My joy will come when I can understand string theory. This is a hurdle I must overcome.

hubot

For people physical aspects of our life is doesn't matter

I feel someway the most comfortable in physics and maths.

0celo7

19:57

@ACuriousMind Huh, I was pretty stupid back then.

@ACuriousMind I agree.

Hari Prasad

@0celo7 Are you so obsessed with string theory?

ACuriousMind

Mar 11 at 22:40, by 0celo7

don't ask me what all of that means, high school me was smarter

0celo7

Nope

Danu

@0celo7 Remember that stuff about facepalming in 4 years?

0celo7

@ACuriousMind smarter about math and physics, but stupider overall

Hari Prasad

20:02

Will humans reach mars by 2035?

hubot

In teachers opinions I'm obsessed on physics.

Is that a bad sign?

Hari Prasad

@hubot Not at all.

0celo7

@Danu no.

@hubot That is very clear.

@hubot Depends.

@ACuriousMind is white a girly color for a car

Bernard Meurer

@0celo7 It's an asshole color

ACuriousMind

I saw that question already and decided to say nothing.

Bernard Meurer

20:04

you might as well use blue sunglasses

blue reflective sunglasses

hubot

My teachers seek to limit physics and giving this as a reward.

I was a little worried.

0celo7

@ACuriousMind please answer

@BernardMeurer takes one to know one

Bernard Meurer

@0celo7 Yeah yeah

Dude I'm telling you, white's a bad color

ACuriousMind

@0celo7 What about "I decided to say nothing" is unclear to you?

Bernard Meurer

why don't you man up and get a silver/grey/black car?

Danu

20:07

@ACuriousMind Why'd you take him off ignore, anyways? ;)

ACuriousMind

@Danu Currently veeeeeery close to correcting that error.

0celo7

Wth

All I want is ACM's opinion

I don't know why he won't help me

ACuriousMind

@0celo7 My opinion is dividing colors into "girly" or "non-girly" is stupid.

0celo7

Oh, of course. Figures.

@ACuriousMind Would you wear a hot pink shirt?

Danu

Always

Bernard Meurer

20:12

@ACuriousMind With a pink shirt: HOT!

ACuriousMind

@0celo7 Depends on the occasion. It's not exactly my style :P

0celo7

@Slereah Did you send that shit to Ellis

Slereah

Not yet

hubot

I have to go!

0celo7

@ACuriousMind yeah, cuz it's girly

0celo7

20:29

@Danu I'm not manly enough to be that confident

Danu

You still care too much

0celo7

What does that mean

Is it pretty standard for Timaeus to write a wall of text that partially addresses one part of the OP?

Does he just spew out paragraphs in a stream of consciousness manner?

Slereah

Well from what I've read of him, yes

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